Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to an apparatus and method for inserting a golf ball precursor product into a thermoset polymer mixture for forming a casting a layer on the golf ball precursor product. More specifically, the present invention relates to an apparatus and method for inserting a core with a boundary layer thereon into a mixture of thermoset polyurethane for casting a thermoset polyurethane cover on the golf ball core and boundary layer.
2. Description of the Related Art
Golf balls may comprise one-piece constructions or they may include several layers including a core, one or more intermediate layers and an outer cover that surrounds any intermediate layer and the core. In multi-component golf balls, there exists an inner core. Often, this core is made by winding a band of elastomeric material about a spherical elastomeric or liquid-filled center. Alternatively, the core may be a unitary spherical core made of a suitable solid elastomeric material. One such material that is conventionally used for the core of golf balls is a base rubber, such as polybutadiene, which is cross-linked with a metal acrylate, such as zinc diacrylate.
In the construction of some multi-component golf balls, an intermediate boundary layer is provided outside and surrounding the core. This intermediate boundary layer is thus disposed between the core and the outer cover of the golf ball.
Located outwardly of the core and any intermediate boundary layer is a cover. The cover is typically made from any number of thermoplastic or thermosetting materials, including thermoplastic resins such as ionomeric, polyester, polyetherester or polyetheramide resins; thermoplastic or thermoset polyurethanes; natural or synthetic rubbers such as balata (natural or synthetic) or polybutadiene; or some combination of the above.
Golf balls are typically manufactured by various molding processes, whether one-component or multicomponent balls. Generally, the core of the golf ball is formed by casting, compression molding, injection molding or the like. If an intermediate boundary layer is desired, one or more intermediate boundary layers are added over the core by any number of molding operations, including casting, compression molding, and/or injection molding. The cover is then formed over the core and intermediate boundary layers, if present, through casting, compression molding, and/or injection molding.
One example of a conventional golf ball manufacturing process is described in U.S. Pat. No. 3,068,522, issued on Dec. 18, 1962 (xe2x80x9cthe ""522 patentxe2x80x9d). The manufacturing process disclosed in the ""522 patent uses a molding press having upper and lower die portions that surround a golf ball core. A retractable seat contacts the golf ball core to place the same in the desired orientation within the die cavity. The cover material is then injected into the die cavity to form the cover of the ball. The ""522 patent further discloses that the timing of the retraction of the retractable seat is critical and depends, in part, on the flow rate of the cover material into the mold cavity. In order to prevent the retardation of the flow rate or pre-hardening of the injected coating material, the ""522 patent teaches that in some instances, it may be necessary to heat the molding dies and pre-heat the golf ball core to a temperature slightly above ambient temperature.
Another example, U.S. Pat. No. 5,194,191 (xe2x80x9cthe ""191 patentxe2x80x9d), issued Mar. 16, 1993 discloses a method of preparing thread-wound golf balls. In the ""191 patent, a rubber thread or material is wound around a frozen core of material to form a core. Immediately thereafter, the core undergoes microwave heating to rapidly thaw the frozen core without heating the rubber thread layer and without moisture condensation taking place on the surface of the core. The method of the ""191 patent allegedly reduces the core thawing time and eliminates the need for a drying step.
These and other current golf ball manufacturing processes continue to suffer from a number of disadvantages. For example, when the outer cover of the golf ball is made from a thermoset material, e.g., thermoset polyurethane, the core and any intermediate boundary layer(s) tend to undergo thermal expansion during the casting of the outer cover, as heat is generated by the exothermic reaction of the thermoset processes used in the formation of the cover. As the cover forms, and before the cover develops sufficient green strength, the thermal expansion of the core and any intermediate boundary layer, in turn, may cause the outer cover of the golf ball to fracture or crack. Although this problem is particularly relevant to covers that are formed of thermoset polyurethane, it is not believed to be limited thereto. Similar problems may arise with other materials and processes.
Cracking is not the only problem with the current conventional methods of manufacturing golf balls. Since a temperature gradient exists between the core, intermediate layer, if any, and the outer cover, the central portion of the ball acts as a heat sink that absorbs heat given off during the cover-making process. In this regard, the reaction that takes place to cure the outer cover takes longer given the cooler temperature in the inner core of the ball. Production cycle times are thus adversely increased.
Consequently, there remains a need for methods of manufacturing golf balls that do not suffer from the above disadvantages. Moreover, a system and method that permits precision centering of a core in relation to a cover is greatly desired.
The present invention provides a method and system for inserting a golf ball precursor product, such as a core with a boundary layer, into a cavity containing a predetermined quantity of thermoset material in an uncured state. The present invention allows for a plurality of golf ball precursor products to be centered within a plurality of cavities containing the thermoset material.
One aspect of the present invention is a method for casting a thermoset layer on each of a plurality of golf ball precursor products. The method includes introducing a flowable material into each of a plurality of cavities disposed on a first mold half, and a second mold half. The flowable material is a thermoset polymer material, precursor thermoset polymer materials, or a mixture thereof. Next, each of the plurality of golf ball precursor products are suctioned from a holding platen using a vacuum cup for each. The holding platen is movable from a hopper position to a suctioning position along a horizontal plane. Each vacuum cup is connected to the locating plate. Next, the first mold half is lifted along a longitudinal pathway from a conveyor position to an insert position. The locating plate is also disposed along the longitudinal pathway. Next, the locating plate with each of the plurality of golf ball precursor products retained in corresponding vacuum cups is lowered toward the first mold half at the insert position. Next, each of the plurality of golf ball precursor products is inserted into a corresponding cavity of the plurality of cavities of the first mold half at the insert position. Next, each of the plurality of golf ball precursor products is released from each of the vacuum cups subsequent to the flowable material gelling to a sufficient viscosity. Next, the first mold half with the plurality of golf ball precursor products therein is lowered to the conveyor position. Then, the first mold half is transferred to a mold assembly station for mating with the second mold half to form a mold assembly to enclose each of the plurality of golf ball precursor products within a spherical cavity to form a thermoset layer on each of the plurality of golf ball precursor products.
The method also includes heating the mold assembly to cure the thermoset layer on each of the golf ball precursor products. The method also includes gelling the thermoset material in each of the plurality of cavities of the first mold half for a period of 10 to 60 seconds prior to inserting each of the golf ball precursor products into each of the plurality of cavities of the first mold half.
The plurality of golf ball precursor products suctioned from the holding platen may be ten, and the plurality of cavities of the first mold half would also be ten. The method may also include elevating each of the golf ball precursor products above the holding platen through flowing of air into each of a plurality of platen cavities that hold each of the golf ball precursor products. The flowable material is preferably a thermoset polyurethane material and precursors therefor, and most preferably a para-phenylene diisocyanate-based polyurethane material.
Another aspect of the present invention is a system for casting a thermoset layer on a golf ball precursor product. The system includes a first mold half, a platen, a locating plate, a lifter, a spacer plate and a source of golf ball precursor products. The platen receives the golf ball precursor products from the source in a predetermined pattern. The locating plate has a plurality of vacuum cups for suctioning a corresponding golf ball precursor product from the platen. The locating plate is also movable along a longitudinal pathway from at least a platen position, an upper limit position and an insertion position. The spacer plate is disposed along the longitudinal pathway and has an aperture for placement of each of the vacuuming cups, with a golf ball precursor product, therethrough. The lifter lifts the first mold half along the longitudinal pathway to the spacer plate for receiving of each of the plurality of golf ball precursor products in a corresponding cavity of the plurality of cavities.
The system may also include means for moving each of plurality of vacuum cups from an insertion position to a retraction position. The system may also include a servo-motor for controlling the vertical movement of the locating plate along the longitudinal pathway. The system may also include means for lifting each of the plurality of golf ball precursor products from corresponding cavities of the platen using a pressurized gas.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.